I am messing around in a program that performs all rendering using a matrix set by gluOrtho2D(). What I would like to do is to rotate a specific texture around the y-axis (0,1,0) so that it looks like the original matrix was provided by gluPerspective() instead. I realize that this is not possible with an orthographic projection matrix and that I will have to set up a new perspective projection matrix. I want the textures I draw to look exactly the same as when drawn with the orthographic matrix, except sometimes when I have rotated them around the y-axis.
So to summarize:
How do I find a perspective projection matrix that is equivalent to a given orthographic matrix when shapes are drawn in the xy-plane, but gives me perspective when not in the xy-plane?